1. Technical Field
The invention relates to a sensor chip, a sensor cartridge, and an analysis apparatus.
2. Related Art
Recently, demand for sensors used in medical diagnoses, the inspection of food, and the like has been increasing, and thus development of sensor technology that implements a sensor that is miniaturized and capable of sensing at high speed has been demanded. In order to respond to such demands, various types of sensors using electrochemical techniques and the like have been reviewed. Among these, from the viewpoint of easy integration, low cost, and low sensitivity to the measurement environment, sensors using surface plasmon resonance (SPR) have drawn attention.
Here, the surface plasmon is an oscillation mode of an electron wave that is coupled with light depending on boundary conditions specific to the surface. As a method of exciting the surface plasmon, there is a method in which a diffraction grating is imprinted on a metal surface and light and plasmon are coupled together or a method in which an evanescent wave is used. For example, as a configuration of a sensor that uses SPR, a configuration in which a total reflection-type prism and a metal film brought into contact with a target substance that is formed on the surface of the prism are included is known. According to such a configuration, whether or not a target substance is adsorbed is detected, including whether or not an antigen is adsorbed in an antigen-antibody reaction and the like.
However, while propagation-type surface plasmon exists on the metal surface, localized-type surface plasmon exists in a metal fine particle. It is known that, when the localized-type surface plasmon, that is, the surface plasmon that exists locally on the microstructure of the surface is excited, a markedly enhanced electric field is generated.
Thus, in order to improve the sensitivity of the sensor, a sensor that uses a localized surface plasmon resonance (LSPR) using metal fine particles or metal nanostructures is proposed. For example, in JP-A-2000-356587, by irradiating light onto a transparent substrate having a surface to which metal fine particles are fixed in a film shape and measuring the absorbance of light being transmitted through the metal fine particles, a change in the medium near the metal fine particles is detected, whereby adsorption or deposition of a target substance is detected.
However, according to JP-A-2000-356587, it is difficult to produce metal fine particles that have a uniform size (dimension or shape) and to regularly arrange the metal fine particles. When the size or the arrangement of the metal fine particles cannot be controlled, there are variations in absorption due to resonance or a resonant wavelength. Accordingly, the width of the absorbance spectrum becomes broad, and the peak intensity decreases. Accordingly, a change in the signal detecting the change in the medium near the metal fine particles is low, and there are limitations on improving the sensitivity of the senor. Therefore, the sensitivity of the sensor is insufficient for use in specifying a substance from the absorbance spectrum or the like.